High pressure hydraulic brake tubes are generally connected to the brake components by using a tube nut with a hole along its axis of rotation and threads on its exterior. More specifically, the tube nut is positioned around the brake tube so that it threads into a port on the brake component and presses against the back of the flare formed on the end of the brake tube. Thus, the tube nut presses a first sealing surface on the flare of the brake tube into contact with a second sealing surface on the port of the brake component. The contact between the sealing surfaces is compressed by a force sufficient to create a metal-to-metal seal to keep high-pressure brake fluid in the brake system.
Historically, the two sealing surfaces have contained imperfections that are compressed during the tube nut torquing process, resulting in both a seal and a microscopic mechanical locking of the two surfaces. This locking effect was enough to resist the twisting tendency that the brake tube may adopt during the torquing process due to the rotation of the nut on the back side of the brake tube flare.
In recent years the sealing surface of the brake tube and the brake component have been made smoother in an effort to improve the initial sealing robustness of the joint in the vehicle assembly plants. The increased smoothness of the surfaces combined with the high contact area may result in a friction couple that does not generate enough resisting torque to prevent the brake tube from twisting with respect to the brake component during the torquing process. Should the brake tube twist during torquing, multiple unintended and undesirable consequences may result. For example, galling metal may occur at the sealing surfaces due to sliding by metal-on-metal under high contact forces. Further, the brake tube may store torsional energy which can contribute to lower loosening torques of the tube nut. In addition the segments of the brake tube may move out of design-intent positions resulting in lower than intended clearances to other vehicle components.
This document relates to a new and improved flare-type brake line assembly that addresses and eliminates this problem. A method of sealing a flare-type brake line assembly that addresses this problem is also disclosed.